The popularity of information services has grown significantly throughout recent years. Popular information services include topics such as sports, weather, news, and up-to-date stock market information, just to mention a few.
Messaging systems that transmit over-the-air information service messages, generally transmit these messages to a designated group of selective call units. Each selective call unit in the group is programmed to receive one or more of these services. The messaging systems transmit these messages utilizing either synchronous or asynchronous protocols, such as, for example, the Flex protocol (Flex is a trademark of Motorola, Inc.) or the POCSAG protocol.
A message conforming to one of these protocols generally is composed of an address field and a data field. The address field includes a group address designating the group of selective call units. The data field includes a combination of subaddresses and information service messages. Each subaddress corresponds to a unique information service message topic, e.g. weather.
Each of the selective call units in turn is programmed to detect the arrival of group messages by matching the address field of the message with an address stored in the selective call unit. Once the arrival of a group message is detected, the selective call units proceed to intercept and process the information services included in the data field. This is accomplished by decoding each subaddress in the data field until an information service, in which the selective call unit has been activated to intercept, has been identified. Hence, for each service (e.g., weather, stock, sports, news, etc.) a subaddress is used to delimit the service within the data field.
It is apparent that transmitting information services in this manner suffers from the disadvantage that a significant amount of overhead (i.e., a subaddress for each information service message) is incurred when many services are transmitted in a group message. As the proliferation of short message services increases, the efficiency of bandwidth utilization in the messaging system decreases; therefore, raising the cost of such services to consumers.
What is needed therefore is a method and apparatus for reducing the overhead of transmitting information service messages to selective call units.